All About Garlic

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Infamous for its distinctive, pungent smell, but prized for its historic role as a highly medicinal vegetable, garlic is a love-it-or-hate-it kind of food. Some people can’t stand it even in soups and stews, while others happily chow down on raw cloves as a snack (and hopefully brush their teeth afterward!).

And then there’s a third group, the people who hate the taste, but feel guilty because they keep reading all about what a superfood it is. Frequently touted benefits of garlic include cancer prevention, lower blood pressure, and lower cholesterol. It’s also traditionally been used as a natural disinfectant, antibacterial, and antifungal medicine.

To some extent, this medicinal tradition has been backed up by lab experiments, but as always, it’s always important to read the research critically – were the studies done in humans, in animals, or in test tubes? Does the benefit rely on choking down 10 cloves of garlic a day, or is it something that a reasonable diet could include? Ultimately, the evidence is neutral to positive: there’s a lot of potential, but very little conclusive research to suggest that otherwise healthy people should worry about eating garlic if they don’t like the taste.

Garlic and Chronic Disease

The most famous chemical in garlic is allicin, a sulfur-containing compound that’s most concentrated in fresh garlic, and becomes even stronger when the garlic is crushed or chewed. This is what gives the garlic such a strong taste and smell. Like many other plant chemicals, allicin functions as the garlic’s defense against predators and pests, and many of garlic’s health benefits come from allicin mounting that exact same defense for your benefit.

Cholesterol and Cardiovascular Health

One of garlic’s most famous benefits has traditionally been the prevention of heart disease, specifically by lowering blood cholesterol and blood pressure. High blood cholesterol is really more of a symptom (the real problem is whatever is causing the high cholesterol), but from a health standpoint, it’s still interesting to see what kinds of treatments reduce cholesterol levels.

In the case of garlic, the evidence is mixed. A 2000 review and analysis concluded that while the available studies suggest a modest benefit, it’s hard to analyze the data accurately because they all used different forms of garlic (powdered, fresh, or extracts).

On the other hand, these effects may only work in the short term: the few studies who followed up to 6 months found no real benefits from garlic compared to placebo. And a study from 2006 demonstrated no benefit in cholesterol levels (or anything else) even in the short-term for garlic powder over a placebo. The most recent meta-analysis, from 2012, was back to finding a small benefit for garlic in whole food, powder, or oil form.

The evidence for blood pressure and other markers of cardiovascular risk is equally inconclusive: some studies find a benefit, and others don’t. Some population studies show that garlic is associated with a lower risk, but this kind of research is so inconclusive that it’s hard to know for sure. So while the evidence is mixed, it’s safe to say that there isn’t an extreme result either way.

Cancer

It’s everyone’s favorite disease to “cause” or “cure” with food, and garlic is no exception. Garlic does seem to treat cancer in test tubes, and even in some animal models, but whether this benefit carries over to humans eating garlic isn’t clear.

Most of the evidence about garlic and cancer is epidemiological (survey studies). A 2001 meta-analysis of the epidemiological research found there’s an association between garlic intake and prevention of stomach and colorectal cancers, but that there simply isn’t enough strong evidence to suggest benefits for any other kind.

This kind of evidence is obviously limited – food recall is unreliable, and epidemiological studies only prove association, not causation. The very few non-epidemiological studies that we have are conflicting, with some finding benefits, and others finding no change. But many of the population surveys did try to control for confounding factors (like the fact that high intake of garlic usually means high intake of other vegetables as well), so the results are worth noting, if not conclusive.

Garlic as an Antimicrobial

Another traditional benefit of garlic came from its antimicrobial effects. One of the oldest-known natural antibiotics, garlic has been used for centuries to treat bacterial, fungal, and parasitic infections. In test tubes, garlic kills all kinds of pathogens, including well-known microbes like staph, E. Coli, and candida. And it seems that this benefit really does carry over to human subjects. For example, one study found that a diluted garlic extract helped children infected with tapeworms recover more quickly. Another showed the benefits of a garlic-based mouthwash in killing the bacteria that cause cavities.

More excitingly, garlic can sometimes help when other drugs can’t. One study found that garlic extract was effective against five multi-drug resistant strains of bacteria. And a group of researchers in Italy found the benefits so compelling that they even suggested garlic as the basis of potential new treatments for multidrug resistant tuberculosis that doesn’t respond to antibiotics.

Applied to the skin, garlic is quite an effective remedy for fungal skin infections like ringworm and athlete’s foot. One study found that a 1% cream of ajoene (an extract of garlic) was actually even better for athlete’s foot than a 1% cream of a conventional antifungal.

Uniquely among antibiotics, garlic also shows some promise as a gut-friendly alternative: there’s some evidence that it doesn’t attack your friendly intestinal flora alongside the bad guys, and it contains prebiotic carbohydrates (inulin) that help feed the good bacteria. And using it extensively in lab tests, researchers have yet to discover a kind of bacteria that develops a resistance to garlic.

These antimicrobial properties make garlic an exciting natural cure for various ills, a kind of culinary medicine. It might be worth a try if you think you have a bacterial overgrowth (such as SIBO or candida). Nothing here suggests that you can cure any and all chronic infections with garlic, or that you should take garlic instead of going to the doctor when you’re sick, but it’s definitely an interesting line of research and something to bear in mind.

How to Eat Garlic

Garlic is a common seasoning in everything from vinaigrettes to meatloaf to soup, but true garlic-lovers are always on the hunt for dishes that showcase the garlic itself. If you haven’t already, try one of these:

Roasted garlic: mix it with butter or use it in another recipe, if you can stop yourself from gobbling it all down straight out of the oven!

Garlic is also the perfect seasoning for green beans and other pan-fried vegetables, like this quick and simple slaw. Just keep the rest of the seasonings simple, and the garlic itself will shine.

Garlic and FODMAPs intolerance

One potential negative of garlic is that it’s very high in FODMAPs, so if you’re FODMAPs-sensitive, the uncomfortable digestive side effects can be very unpleasant. But there is actually a way to get many of these benefits without the discomfort, because the allicin in garlic is simple to extract yourself at home. In fact, you might already be doing it!

To remove the allicin from garlic, simply crush a garlic clove, let it sit for 5-10 minutes (this increases the concentration of allicin), and then fry the garlic in some hot oil. Remove the garlic and throw it out, but use the oil in any recipe you like: the allicin is fat-soluble, so it will leak out into the oil, but the water-soluble FODMAPs carbohydrates will stay in the garlic clove that you throw away.

Garlic: Conclusions

“Garlic is reasonably good for you” doesn’t make for a great headline, but unfortunately, it’s the truth. Its long history as a folk remedy is a point in its favor, but just because it’s traditional doesn’t mean it’s effective. For cardiovascular health and cancer, the study results are cautiously optimistic at best.

The antimicrobial properties are on more solid footing: garlic is not a replacement for penicillin or any other antibiotic, but it’s showing a lot of promise as a useful co-therapy, especially for skin infections and antibiotic-resistant drugs. In this case, it turns out that the folk remedy really is justified. As an all-natural medicine, garlic completely deserves its time in the spotlight.

So the benefits exist, but they’re not overwhelming. If you love garlic in everything, you can feel good about adding another one of many healthy foods to your diet. If you hate it, don’t feel bad about taking a pass.